The present invention relates to a multi-cylinder internal combustion engine which is capable of regulating the number of cylinders in operation by shifting a given number of cylinders to rest, and aims to obviate shocks caused by fluctuation in the output at the time of such switching.
There have been known in prior art multi-cylinder engines which can increase the combustion efficiency of cylinders in operation to prevent toxic exhaust gas or which can reduce pumping loss through an increase in load rate to better fuel economy, by shifting the number of operating cylinders from the total number at low-load to a given number. There are conventionally known various methods for suspending the operation of cylinders such as disclosed in U.S. Pat. Nos. 4,221,200, and 4,221,201 and BP 2,075,118. In one of such methods, the operation of the intake and exhaust valves(s) is suspended; it is also known to stop the operation of a fuel supply system provided for each cylinder (in many cases an electrically controlled fuel injection valve provided on branched pipes of the intake manifold) or the like.
These multi-cylinder engines, however, are defective in that the output of the engine would fluctuate when the operation of cylinders is suspended, and when carried on automotive vehicles, it might cause a shock, presenting difficulties in smooth driving. Such switching methods further involve a complicated control means.